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采用种子乳液聚合法制备了聚丙烯酸丁酯(PBA)乳液,然后通过第二单体甲基丙烯酸甲酯的预溶胀法聚合制备了PBA/聚甲基丙烯酸甲酯(PMMA)乳液,用激光散射粒度仪和透射电子显微镜对乳液粒径和结构进行了表征.结果表明,当乳化剂十二烷基硫酸钠质量分数为丙烯酸丁酯的1.5%时,可制备粒径为53.6 nm且分布窄的PBA种子乳液;通过调整补加乳化剂、单体与种子乳液的用量,可制得粒径为53.6~443.8 nm的一系列单分散PBA乳液;PBA/PMMA乳液具有完善的核壳结构,且在核壳两相间存在着一个过渡层. 相似文献
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悬浮-乳液耦合聚合制备大粒径核-壳结构PS/PMMA复合粒子 总被引:2,自引:1,他引:1
采用在苯乙烯(St)悬浮聚合不同时期滴加甲基丙烯酸甲酯(MMA)乳液聚合组分的悬浮-乳液耦合聚合方法,制备大粒径核-壳结构复合粒子。研究发现:在St悬浮聚合初期和宏观成粒基本完成的聚合后期滴加MMA乳液聚合组分,分别得到由初级粒子凝并的非核-壳结构粒子和核-壳结构不完整的复合粒子,粒径分布较宽;在St悬浮聚合中期滴加MMA乳液聚合组分,MMA和PMMA乳胶粒子易于向PS粒子扩散或粘并,制备得到平均粒径大于100gm、粒径分布窄和核-壳结构良好的PS/PMMA复合粒子。 相似文献
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以聚丙烯酸丁酯(PBA)为内核,通过种子乳液聚合制备了分别以聚甲基丙烯酸甲酯(PMMA)、聚氯乙烯(PVC)、PMMA/PVC为壳层的纯丙烯酸酯(ACR)和PVC改性ACR乳液.扫描电镜观察发现,纯ACR乳胶粒子具有明显的核-壳结构,进一步包覆PVC后形成疏松外层.考察了不同结构ACR与PVC共混物的相态结构、抗冲性能和断面形貌,发现用PVC部分或完全替代PMMA壳层的改性ACR在PVC基体分散良好,具有与纯ACR相当的增韧PVC作用,冲击断面呈现典型的韧性断裂特征. 相似文献
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周应学 《化学推进剂与高分子材料》2009,7(3):46-48
由种子乳液聚合法制备了聚苯乙烯-聚甲基丙烯酸甲酯核-壳粒子。以过硫酸钾(KPS)为引发剂,分别以非离子型辛基酚聚氧乙烯醚(OP—10)和复合十二烷基硫酸钠(SDS)/OP—10(质量比为1:4)为乳化剂,合成了聚苯乙烯种子核。连续滴加甲基丙烯酸甲酯(MMA),以OP—10乳化的种子乳液可以制备粒径范围在0.16~0.67μm的核-壳粒子,当单体苯乙烯与甲基丙烯酸甲酯(St/MMA)的质量比为3:7时,所得粒径为0.18μm,粒径分散系数为0.012。而以OP-10/SDS质量比为4:1制备的种子乳液所得核壳粒子直径在毫米级。差示扫描量热研究显示,以OP-10乳化所得种子乳液制衢的复合粒子的玻璃化转变温度为97.2℃,峰形单一,表现山良好的热性能。 相似文献
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A-187改性核壳型聚丙烯酸酯乳液的制备及性能表征 总被引:2,自引:0,他引:2
以甲基丙烯酸甲酯、丙烯酸丁酯、丙烯酸-2-乙基己酯、γ-(2,3-环氧丙氧基)丙基三甲氧基硅烷(A-187)等为原料,过硫酸铵为引发剂,通过种子乳液聚合法制备了具有核-壳结构的A-187改性聚丙烯酸酯(SACR)系列微复合高分子乳液。表征了乳胶粒子的结构形态及粒度分布,测定了聚合物的玻璃化转变温度、拉伸强度和聚合物薄膜的吸水率。所得SACR系列微复合聚合物乳液的乳胶粒子具有核壳结构,粒径分布较窄,聚合物的玻璃化转变温度随A-187加量的增加有所升高,聚合物的力学性能和聚合物的耐水性能有所改善。 相似文献
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A new ampholytic homopolypeptide, , which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO4 and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu2+ and Ca2+, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu2+ complex near 240 nm. Dependence of the peak intensity on pH at various q values () indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu2+ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu2+ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu2+-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation. 相似文献
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Silvia Schicker Daniel E. García Igor Gorlov Rolf Janssen Nils Claussen 《Journal of the American Ceramic Society》1999,82(10):2607-2612
Wet milling of Al2 O3 -aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al2 O3 and Fe2 O3 /Al/Al2 O3 powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe2 O3 /Al/Al2 O3 powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al2 O3 powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8. 相似文献
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Akira Akimoto 《Polymer》1974,15(4):216-218
The polymerization of vinyl chloride has been investigated using an catalyst system in the presence of various Lewis bases. Effective Lewis bases are γ-butyrolactone, diglyme and diethylenetriamine which are multidentate. The rate of polymerization is dependent not only on the basicity of the Lewis base used but also on a coordination number of one. The latter is the predominant factor. For the effect of polymeric amines, a tentative hypothesis is discussed. 相似文献
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Sintering kinetics of the system Si3 N4-Y2O3 -Al2 O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si3 N4 were studied with additions of 4 to 17 wt% Y2 O3 and 4 wt% A12 O3 . Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si3 N4 and glass or β '-Si3 N4 , α '-Si3 N4 , and glass. The compositions and amounts of the residual glassy phases are estimated. 相似文献
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Mats Carlsson Mats Johnsson Mats Nygren 《Journal of the American Ceramic Society》1999,82(8):1969-1976
Ta0.33 Ti0.33 Nb0.33 C and Ta0.33 Ti0.33 Nb0.33 C x N1− x whiskers were synthesized via a carbothermal vapor-liquid-solid growth mechanism in the temperature range 900°-1450°C in Ar or N2 . The optimum temperature was 1250°C. Whiskers were obtained in a yield of 70-90 vol%. The whiskers were 0.5–1 µm in diameter and 10–30 µm in length. The starting materials that produced the highest whisker yield were: TiO2 , Ta2 O5 , Nb2 O5 , C, Ni, and NaCl. C was added to reduce the oxides, and Ni to catalyze whisker growth. NaCl was used as a source of Cl for vapor-phase transportation of Ta and Nb oxochlorides and Ti chlorides to the catalyst. The catalyst metal was recycled several times during the synthesis and was transported as NiCl2 ( g ) according to thermodynamic calculations. The rate of formation and the chemical composition of the whiskers depended on the synthesis temperature, the choice of catalyst, and the atmosphere. At low temperatures, the whiskers were enriched in Nb and Ta, whereas the Ti content increased with increased synthesis temperature. 相似文献